Electropneumatic control valve comprising a guide arrangement for a control piston

ABSTRACT

Electropneumatic control valve for a pneumatic brake system of a vehicle having a relay valve housing in which an axially adjustable control piston is arranged for actuating a valve seat arrangement which switches the compressed-air flow between at least one exterior brake line connection, a supply pressure connection and a bleeder connection. The control piston is axially guided by means of a coaxial guiding arrangement. The guiding arrangement comprises a separate guiding sleeve which is stationarily fastened to the pilot valve housing and which is provided with an upper guiding section which, for the axial guidance, corresponds with a passage bore in the control piston, and which, in addition, has a lower tube section of a smaller outside diameter adjoining the upper guiding section in order to guide the outgoing air flowing through an integrated axial bleeder duct directly to the bleeder connection.

This application claims the priority of German application 101 20 321.7,filed Apr. 26, 2001, the disclosure of which is expressly incorporatedby reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an electropneumatic control valve for apneumatic brake system of a vehicle.

The electropneumatic valve of the present invention has a relay valvehousing in which an axially adjustable control piston is arranged foractuating a valve seat arrangement which switches the compressed-airflow between at least one exterior brake line connection, a supplypressure connection and a bleeder connection. The control piston of thecontrol valve is axially guided by means of a guiding arrangement andcan be acted upon by a control pressure by way of at least oneelectromagnetic pilot valve for the axial adjustment. The pilot valve isaccommodated in a pilot valve housing connected with the relay valvehousing. The present invention specifically relates to a specialconstructive design of the guiding arrangement of the control piston.

A control valve of the above-mentioned type is used within a pneumaticbrake system of a vehicle in order to control a brake pressurecorresponding to the desired braking effect. For this purpose, a brakeline originating from the control valve is usually connected with abrake cylinder at the vehicle wheel, which brake cylinder generates thebraking force required for the braking of the vehicle wheel for a diskor drum brake connected thereto. The defining of the desired pressurevalue for the electropneumatic control valve can take place electricallyas well as pneumatically. However, the pneumatic control is mostlyutilized only for safety purposes in the event of a failure of theelectric control.

An electropneumatic control valve of this type is known from GermanPatent Document DE 39 31 761 C2. The control valve has a large-surfacecontrol piston which is accommodated in an axially displaceable mannerinside a cylindrical hollow space of a relay valve housing. The controlpiston separates the hollow space into a control chamber and into aworking chamber. In the case of the working chamber, a coaxial hollowpin is constructed on the control piston, which hollow pin is used foractuating an adjacent valve seat arrangement. By means of an axialadjustment of a spring-braced valve tube, the valve seat arrangementswitches the compressed-air flow between an exterior brake lineconnection, a supply pressure connection as well as a bleederconnection.

By means of a pilot valve arrangement, the control piston can be actedupon by a control pressure on the control chamber. The pilot valvearrangement consists of two electropneumatic pilot valves which, bymeans of a coordinated energizing of the integrated electric coils,cause a rising, maintaining or lowering of the control pressure withinthe control chamber in order to implement the desired movement of thecontrol piston while interacting with the restoring spring arranged onthe opposite side of the control piston.

The axial guidance required because of the large-surface characteristicof the control piston is achieved here by way of a coaxial guide bore inthe pilot valve housing, which guide bore corresponds with a guiding pincoaxially shaped to the control piston.

However, this type of guidance has the disadvantage that the guide borein the pilot valve housing must be produced in a highly precise mannerand with a high surface quality in order to avoid a jamming or tiltingof the control piston within the cylindrical hollow space during theoperation. Furthermore, this known guiding arrangement causes arelatively complicated shaping of the control piston whose productiontherefore requires high expenditures. This applies particularly also tothe making of the passage bore which extends coaxially through thecontrol piston and is used for discharging outgoing air from the controlchamber to the bleeder connection. Here, the passage bore has arelatively large diameter in order to permit a fast bleeding of thecontrol chamber.

In practice, it has been attempted to design a guiding arrangement forthe control piston according to another, constructively simplerprinciple, which is known from German Patent Document DE 196 05 562 A1.In that case, a sleeve is used for the guidance, which sleeve is joinedinto a suitable coaxial recess of the pilot valve. By way of the outsidediameter of the sleeve projecting from the pilot valve housing in thismanner, the control piston is guided by way of a corresponding coaxialpassage bore for this purpose.

The fastening of the sleeve on the pilot valve housing takes place witha radial play and/or swivel play for the compensation of aproduction-caused play between the control piston and the pilot valvehousing. However, this type of guidance of the control piston results ina deterioration of the guiding characteristics because a tilting of thecontrol piston becomes possible as a result of the swivel play and/orradial play.

Furthermore, the guiding principle applied here requires a small spacefor the passage bore for discharging the outgoing air from the controlchamber. To this extent, only a comparatively small effectivecross-section is possible.

It is therefore an object of the present invention to improve anelectropneumatic control valve of the above-described type such that aprecise guiding of the control piston can be carried out with aneffective integrated guiding of outgoing air at low manufacturingexpenditures.

The object is achieved by an electropneumatic control valve of thepresent invention having a relay valve housing in which an axiallyadjustable control piston is arranged for actuating a valve seatarrangement which switches the compressed-air flow between at least oneexterior brake line connection, a supply pressure connection and ableeder connection. The control piston is axially guided by means of acoaxial guiding arrangement and capable of being acted upon by a controlpressure by way of at least one electromagnetic pilot valve for theaxial adjustment. The pilot valve is accommodated in a pilot valvehousing connected with the relay valve housing. The guiding arrangementof the control piston comprises a separate guiding sleeve which isstationarily fastened to the pilot valve housing and which is providedwith an upper guiding section which, for the axial guidance, correspondswith a passage bore in the control piston, and which, in addition, has alower tube section of a smaller outside diameter adjoining the upperguiding section in order to guide the outgoing air flowing through anintegrated axial bleeder duct over the area of the valve seatarrangement directly to the bleeder connection.

The invention includes the technical teaching that the guidingarrangement of the control piston consists of a separate guiding sleevewhich is fastened to the pilot valve housing and which is provided withan upper guiding section which, for the axial guidance, corresponds witha passage bore in the control piston and which, in addition, has a lowertube section of a smaller outside diameter which adjoins the upperguiding section in order to guide the outgoing air flowing through anintegrated axial bleeder duct over the area of the valve seatarrangement directly to the bleeder connection.

The advantage of the invention is particularly the special furtherdevelopment of the guiding sleeve to be used, which provides a preciseguiding function for the control piston as well as an effectiveoutgoing-air guidance. Because of the particularly long bleeder ductwhich extends directly to the bleeder connection over the area of thevalve seat arrangement, the opening of the bleeder duct arrives in anarea of a lower ram pressure, whereby, because of the low existingcounterpressure in the proximity of the bleeder connection, a bleedingof the control chamber is achieved which is faster despite the relativesmall diameter of the bleeder duct. Surprisingly, the tube sectionsituated in the outgoing-air flow of the working chamber results in anextreme noise reduction during the bleeding of the brake line.

In order to further minimize the noise caused by the outflowing air atthe electropneumatic control valve, a sound absorber can, in addition,be mounted on the bleeder connection. In cooperation with the soundabsorber, the distal end of the tube section of the guiding sleeve has afissured construction in order to ensure a free flowing-out of theoutgoing air from the bleeder duct. As a result of this arrangement, avery low noise level is achieved on the whole which meets even strictrequirements with respect to a control valve of the above-mentionedtype.

Preferably, the guiding sleeve according to the invention, at least inthe area of the guiding section, consists of a plastic material with alow sliding friction coefficient. As a result, a low sliding friction isachieved which is favorable for the axial guidance because the controlpiston, as a friction partner, preferably is also produced of a plasticmaterial. It is also conceivable to use different pairings of material.The corresponding passage bore in the control piston, to this extent,can also be equipped with a Teflon bush or the like.

According to another embodiment of the invention, a guide pin formed inthe pilot valve housing is provided for fastening the guiding sleeve, inwhich case, by way of a force-locking press fit, a connection with theguiding sleeve is established. Corresponding with the guide pin, in thearea of the guiding section, the guiding sleeve preferably has acylindrical recess of a larger diameter, which extends essentiallycoaxially with respect to the bleeder duct, by means of which recess,the fastening takes place by a pressing onto the guide pin. Since it issufficient in this case to provide only two axially spaced, ring-shapedfitting sections inside the recess, which fitting sections come to reston the guide pin, because of the minimized pressing-on force, thispressing-on can also take place manually. In addition, the two spacedring-shaped fitting sections ensure a precise positioning of the guidingsleeve with respect to the guide pin.

According to another advantageous embodiment of the guiding sleeve, astep is constructed in the distal end area of the tube section in orderto permit an end-side form-locking fixing of the guiding sleeve in astationary manner with respect to the relay valve housing. As a result,despite the large length, the guiding sleeve is securely fixed insidethe relay valve housing at both ends, specifically in the upper area ofthe recess as well as in the lower area of the opening of the bleederduct.

In order to permit a particularly fast flowing of the outgoing air outof the bleeder duct, it is advantageous for the flow cross-section ofthe bleeder duct to be maximal. However, a minimal required wallthickness of the tube section should be retained in order to ensure asufficient stability of the tube section. The outside diameter of thetube section, in turn, is limited by a minimally required ring gap forthe outgoing air from the brake line when the latter is bled. In orderto meet all these requirements, the wall of the tube section canadditionally be reinforced by a ring arrangement, so that the requiredwall thickness as well as the overall diameter of the tube section canbe kept as small as possible and a sufficient stability is neverthelessachieved. The rib arrangement preferably consists of several shaped-onribs extending axially along the outside wall of the tube section. Theshaped-on ribs are aligned essentially axially parallel with respect tothe tube section and, in the cross-sectional view, are arranged at anequal distance from one another. The result is therefore a star-typeshape in a cross-sectional view.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of an electropneumatic controlvalve with a guiding arrangement for the interior control pistonaccording to one embodiment of the invention;

FIG. 2 is a longitudinal sectional view of the guiding sleeve used inthe case of the guiding arrangement illustrated in FIG. 1; and

FIG. 3 is a cross-sectional view of the guiding sleeve of FIG. 1 in thearea of the tube section.

DETAILED DESCRIPTION OF THE DRAWINGS

The electropneumatic control valve according to FIG. 1 has a housingarrangement which is essentially constructed in two parts and whichconsists of a lower relay valve housing 1 which is connected with anupper pilot valve housing 2, with sealing element 3 situated in-between.The connection takes place by means of a (not shown) screwed connection.The relay valve housing 1 and the pilot valve housing 2 enclose aninterior control chamber 4 in which a control piston 5 is axiallymovably arranged. For the axial adjustment of the control piston 5, apilot valve arrangement is used which is accommodated in the pilot valvehousing 2 and of which only a pilot valve 6 is illustrated here. Thepilot valve arrangement is electrically controlled here by means of anelectronic unit. The illustrated pilot valve 6 is used as an outletvalve and, when operated, bleeds the control chamber 4, in which casethe outgoing air is discharged to the atmosphere. In addition, a secondpilot valve (not shown) exists which is the inlet valve and which isused for acting upon the control chamber 4 by means of a controlpressure in order to move the control piston 5.

When acting upon the control chamber 4, the control piston 5 actuates avalve set arrangement 8 by way of a lower sleeve-type extension. Thevalve seat arrangement 8 essentially consists of a closing element 9which, by means of the force of a restoring spring 10, is pressedagainst two concentrically arranged adjacent valve seats. By means ofthe latter, the compressed-air flow can be switched between a brake lineconnection 11 arranged on the relay valve housing 1, on the one hand, asupply pressure connection (not visible here)—which is connected with aninternal supply pressure chamber 12- and a bleeder connection 13, on theother hand. The bleeder connection 13 is additionally provided with asound absorber 14 for reducing noise.

The electropneumatic control valve is illustrated here in its closed-offswitching position. When the control chamber 4 is acted upon by means ofa control pressure and during the subsequent movement of the controlpiston 5 in the direction of a lower position, a compressed-air flowtakes place by opening the exterior valve seat of the valve seatarrangement 8, originating from the supply pressure chamber 12 to aworking chamber 15, which leads in at the brake line connection 11 inorder to thereby increase the brake pressure.

During a bleeding of the control chamber 4, the control piston 5 ischanged into an upper position, in which case the interior valve seat ofthe valve seat arrangement 8 is opened, so that, originating from thebrake line connection 11, compressed air arrives at the bleederconnection 13 by way of the working chamber 15 in order tocorrespondingly lower the brake pressure. As a result, the brakepressure is influenced by a reciprocal movement of the control piston 5.In the central closed-off switching position, no compressed-air flowtakes place.

The large-surface control piston 5 is axially guided by way of a coaxialguiding arrangement. The guiding arrangement of the control piston 5consists of a guiding sleeve 17 mounted on a guide pin 16 of the pilotvalve housing 2, which guiding sleeve 17 slidingly interacts with acentral passage bore 18 in the control piston 5 while forming an axialguide.

As illustrated in detail in FIG. 2, the guiding sleeve 17 consists of anupper guiding section 19, which is coaxially adjoined by a lower tubesection 20. With respect to the guiding section 19, the lower tubesection 20 is constructed with a smaller outside diameter. The guidingsleeve 17 is constructed in one piece and is produced of a plasticmaterial by means of injection molding. A bleeder duct 21 extendscoaxially through the guiding sleeve 17 and guides the outgoing airoccurring when the control chamber 4 (not shown here) is bled, directlyto the bleeder connection 13. In the area of the guiding section 19, thebleeder duct 21 is constructed to form a recess 22 of a larger diameter.By way of the recess 22, the guiding sleeve 17 is fastened to the (notshown) hollow guide pin 16. Two axially spaced ring-shaped fittingsections 23 a and 23 b are provided inside the recess 22. The twofitting sections 23 a, 23 b come to rest directly on sections of theguide pin 16 manufactured with an accurate fit in order to ensure aprecise positioning of the two components of the guiding arrangement tobe mutually connected.

In the distal end area of the tube section 20, a step 24 is constructedwhich form-lockingly interacts with the relay valve housing 1 (not shownhere) in order to position this end area of the tube section 20 in anexact manner. The end of the tube section 20 situated here isconstructed to be fissured in the manner of a cross recess as a resultof a groove arrangement 25 in order to permit an unhindered flowing-outof the outgoing air emerging from the bleeder duct 21.

According to FIG. 3, the wall of the tube section 20 is reinforced byway of a rib arrangement. Here, the rib arrangement consists of fourshaped-on ribs 26 a to 26 d extending axially along the exterior wall ofthe tube section 20, which shaped-on ribs 26 a to 26 d are arranged atan equal mutual distance, that is, in a cross shape. By means of thisrib arrangement, a sufficient stability of the tube section 20 isachieved while the flow cross-section is simultaneously maximized.

The invention is not limited to the above-indicated preferredembodiment. Modifications thereof are also conceivable which may fallinto the scope of protection of the claims which follow. In particular,the invention is not limited to a two-part housing arrangement for theelectropneumatic control valve. A one-part housing arrangement is alsoconceivable. Here, the relay valve housing and the pilot valve housingwill then form sections of the one-piece housing arrangement. Likewise,a housing arrangement consisting of more than two parts is alsoconceivable.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. Electropneumatic control valve for a pneumatic brake system of avehicle having a relay valve housing in which an axially adjustablecontrol piston is arranged for actuating a valve seat arrangement whichswitches the compressed-air flow between at least one exterior brakeline connection, a supply pressure connection as well as a bleederconnection, the control piston being axially guided via a coaxialguiding arrangement and being capable of being acted upon by a controlpressure by way of at least one electromagnetic pilot valve for theaxial adjustment, which pilot valve is accommodated in a pilot valvehousing connected with the relay valve housing, wherein the guidingarrangement of the control piston comprises a separate guiding sleevewhich is stationarily fastened to the pilot valve housing and which isprovided with an upper guiding section which, for the axial guidance,corresponds with a passage bore in the control piston, and which, inaddition, has a lower tube section of a smaller outside diameteradjoining the upper guiding section in order to guide the outgoing airflowing through an integrated axial bleeder duct over the area of thevalve seat arrangement directly to the bleeder connection. 2.Electropneumatic control valve according to claim 1, wherein the bleederconnection is provided with a sound absorber in order to minimize thesound caused by the outflowing air.
 3. Electropneumatic control valveaccording to claim 1, wherein the guiding sleeve consists of a plasticmaterial with a low coefficient of sliding friction at least in the areaof the guiding section.
 4. Electropneumatic control valve for apneumatic brake system of a vehicle having a relay valve housing inwhich an axially adjustable control piston is arranged for actuating avalve seat arrangement which switches the compressed-air flow between atleast one exterior brake line connection, a supply pressure connectionas well as a bleeder connection, the control piston being axially guidedvia a coaxial guiding arrangement and being capable of being acted uponby a control pressure by way of at least one electromagnetic pilot valvefor the axial adjustment, which pilot valve is accommodated in a pilotvalve housing connected with the relay valve housing, wherein theguiding arrangement of the control piston comprises a separate guidingsleeve which is stationarily fastened to the pilot valve housing andwhich is provided with an upper guiding section which, for the axialguidance, corresponds with a passage bore in the control piston, andwhich, in addition, has a lower tube section of a smaller outsidediameter adjoining the upper guiding section in order to guide theoutgoing air flowing through an integrated axial bleeder duct over thearea of the valve seat arrangement directly to the bleeder connection,and for the fastening of the guiding sleeve on the pilot valve housing,a hollow guide pin is provided which is shaped thereto and which, by wayof a force-locking press fit, establishes a connection with the guidingsleeve.
 5. Electropneumatic control valve according to claim 4, wherein,in the area of the guiding section, the guiding sleeve has a recess of alarger diameter which extends essentially coaxial with respect to thebleeder duct, by way of which recess the fastening takes place by apressing onto the guide pin.
 6. Electropneumatic control valve accordingto claim 5, wherein two axially spaced ring-shaped fitting sections areprovided inside the recess, which fitting sections come to rest on theguide pin during the pressing-on.
 7. Electropneumatic control valve fora pneumatic brake system of a vehicle having a relay valve housing inwhich an axially adjustable control piston is arranged for actuating avalve seat arrangement which switches the compressed-air flow between atleast one exterior brake line connection, a supply pressure connectionas well as a bleeder connection, the control piston being axially guidedvia a coaxial guiding arrangement and being capable of being acted uponby a control pressure by way of at least one electromagnetic pilot valvefor the axial adjustment, which pilot valve is accommodated in a pilotvalve housing connected with the relay valve housing, wherein theguiding arrangement of the control piston comprises a separate guidingsleeve which is stationarily fastened to the pilot valve housing andwhich is provided with an upper guiding section which, for the axialguidance, wherein corresponds with a passage bore in the control piston,and which, in addition, has a lower tube section of a smaller outsidediameter adjoining the upper guiding section in order to guide theoutgoing air flowing through an integrated axial bleeder duct over thearea of the valve seat arrangement directly to the bleeder connection,and a step is constructed in the distal end area of the tube section, inorder to thereby permit an end-side form-locking fixing of the guidingsleeve stationarily with respect to the relay valve housing. 8.Electropneumatic control valve for a pneumatic brake system of a vehiclehaving a relay valve housing in which an axially adjustable controlpiston is arranged for actuating a valve seat arrangement which switchesthe compressed-air flow between at least one exterior brake lineconnection, a supply pressure connection as well as a bleederconnection, the control piston being axially guided via a coaxialguiding arrangement and being capable of being acted upon by a controlpressure by way of at least one electromagnetic pilot valve for theaxial adjustment, which pilot valve is accommodated in a pilot valvehousing connected with the relay valve housing, wherein wherein theguiding arrangement of the control piston comprises a separate guidingsleeve which is stationarily fastened to the pilot valve housing andwhich is provided with an upper guiding section which, for the axialguidance, corresponds with a passage bore in the control piston, andwhich, in addition, has a lower tube section of a smaller outsidediameter adjoining the upper guiding section in order to guide theoutgoing air flowing through an integrated axial bleeder duct over thearea of the valve seat arrangement directly to the bleeder connection,and the distal end of the tube section has a fissured construction inorder to ensure an unhindered outflow of the outgoing air emerging fromthe bleeder duct.
 9. Electropneumatic control valve for a pneumaticbrake system of a vehicle having a relay valve housing in which anaxially adjustable control piston is arranged for actuating a valve seatarrangement which switches the compressed-air flow between at least oneexterior brake line connection, a supply pressure connection as well asa bleeder connection, the control piston being axially guided via acoaxial guiding arrangement and being capable of being acted upon by acontrol pressure by way of at least one electromagnetic pilot valve forthe axial adjustment, which pilot valve is accommodated in a pilot valvehousing connected with the relay valve housing, wherein the guidingarrangement of the control piston comprises a separate guiding sleevewhich is stationarily fastened to the pilot valve housing and which isprovided with an upper guiding section which, for the axial guidance,corresponds with a passage bore in the control piston, and which, inaddition, has a lower tube section of a smaller outside diameteradjoining the upper guiding section in order to guide the outgoing airflowing through an integrated axial bleeder duct over the area of thevalve seat arrangement directly to the bleeder connection, and formaximizing the flow cross-section of the bleeder duct, the wall of thetube section is reinforced by way of a rib arrangement, so that therequired wall thickness as well as the total diameter in the area of thetube section are minimal.
 10. Electropneumatic control valve accordingto claim 9, wherein the rib arrangement consists of at least fourintegral ribs which extend axially along the exterior wall of the tubesection, are aligned essentially axially parallel with respect to thetube section and, in the cross-sectional view, are arranged at an equaldistance from one another.
 11. An electropneumatic control valve for apneumatic brake system of a vehicle, comprising: a valve housingincluding relay valve housing portion and a pilot valve housing portion;and a control piston slidably disposed in the valve housing and adaptedto be actuated by a pilot valve arrangement in the pilot valve housingto actuate an interior valve seat arrangement in the relay valve housingin order to switch compressed air flow between an exterior brake lineconnection, a supply pressure connection and a bleeder connection,wherein the control piston includes an axial central passage whichcooperates with a coaxial guiding sleeve affixed to the pilot valvehousing, the guiding sleeve includes an upper guiding section, a lowertube section with an outer diameter smaller than an outer diameter ofthe upper guiding section, and an axial guiding sleeve bleeder duct incommunication with a pilot valve housing bleeder duct, and the lowertube section cooperates with the relay valve interior valve seatarrangement to guide air flowing through the guiding sleeve bleeder ductto the bleeder connection.
 12. The electropneumatic control valve ofclaim 11, further comprising: a sound absorber which minimizes soundcaused by air flow through the bleeder connection.
 13. Theelectropneumatic control valve of claim 11, wherein the guiding sleevecomprises a material with a low coefficient of sliding friction at leastin the area of the upper guiding section.
 14. The electropneumaticcontrol valve of claim 13, wherein the low friction material is aplastic material.
 15. An electropneumatic control valve for a pneumaticbrake system of a vehicle, comprising: a valve housing including relayvalve housing portion and a pilot valve housing portion; and a controlpiston slidably disposed in the valve housing and adapted to be actuatedby a pilot valve arrangement in the pilot valve housing to actuate aninterior valve seat arrangement in the relay valve housing in order toswitch compressed air flow between an exterior brake line connection, asupply pressure connection and a bleeder connection, wherein the controlpiston includes an axial central passage which cooperates with a coaxialguiding sleeve affixed to the pilot valve housing, the guiding sleeveincludes an upper guiding section, a lower tube section with an outerdiameter smaller than an outer diameter of the upper guiding section,and an axial guiding sleeve bleeder duct in communication with a pilotvalve housing bleeder duct, the lower tube section cooperates with therelay valve interior valve seat arrangement to guide air flowing throughthe guiding sleeve bleeder duct to the bleeder connection, and theguiding sleeve is affixed to the pilot valve housing by press-fit onto ahollow guide pin projecting from the pilot valve housing.
 16. Theelectropneumatic control valve according to claim 15, wherein the upperguiding portion of the guiding sleeve has a recess coaxial to theguiding sleeve bleeder duct, said recess having a larger diameter thanthe bleeder duct and shaped to receive the guide pin.
 17. Theelectropneumatic control valve according to claim 16, wherein at leasttwo circumferential portions of the recess frictionally engage the guidepin.
 18. An electropneumatic control valve for a pneumatic brake systemof a vehicle, comprising: a valve housing including relay valve housingportion and a pilot valve housing portion; and a control piston slidablydisposed in the valve housing and adapted to be actuated by a pilotvalve arrangement in the pilot valve housing to actuate an interiorvalve seat arrangement in the relay valve housing in order to switchcompressed air flow between an exterior brake line connection, a supplypressure connection and a bleeder connection, wherein the control pistonincludes an axial central passage which cooperates with a coaxialguiding sleeve affixed to the pilot valve housing, the guiding sleeveincludes an upper guiding section, a lower tube section with an outerdiameter smaller than an outer diameter of the upper guiding section,and an axial guiding sleeve bleeder duct in communication with a pilotvalve housing bleeder duct, the lower tube section cooperates with therelay valve interior valve seat arrangement to guide air flowing throughthe guiding sleeve bleeder duct to the bleeder connection, and a distalend of the lower tube section includes a step which engages acorresponding receiver in the relay valve housing.
 19. Anelectropneumatic control valve for a pneumatic brake system of avehicle, comprising: a valve housing including relay valve housingportion and a pilot valve housing portion; and a control piston slidablydisposed in the valve housing and adapted to be actuated by a pilotvalve arrangement in the pilot valve housing to actuate an interiorvalve seat arrangement in the relay valve housing in order to switchcompressed air flow between an exterior brake line connection, a supplypressure connection and a bleeder connection, wherein the control pistonincludes an axial central passage which cooperates with a coaxialguiding sleeve affixed to the pilot valve housing, the guiding sleeveincludes an upper guiding section, a lower tube section with an outerdiameter smaller than an outer diameter of the upper guiding section,and an axial guiding sleeve bleeder duct in communication with a pilotvalve housing bleeder duct, the lower tube section cooperates with therelay valve interior valve seat arrangement to guide air flowing throughthe guiding sleeve bleeder duct to the bleeder connection, and the lowertube section distal end includes a transverse air flow passage whichintersects the guiding sleeve bleeder duct.
 20. An electropneumaticcontrol valve for a pneumatic brake system of a vehicle, comprising: avalve housing including relay valve housing portion and a pilot valvehousing portion; and a control piston slidably disposed in the valvehousing and adapted to be actuated by a pilot valve arrangement in thepilot valve housing to actuate an interior valve seat arrangement in therelay valve housing in order to switch compressed air flow between anexterior brake line connection, a supply pressure connection and ableeder connection, wherein the control piston includes an axial centralpassage which cooperates with a coaxial guiding sleeve affixed to thepilot valve housing, the guiding sleeve includes an upper guidingsection, a lower tube section with an outer diameter smaller than anouter diameter of the upper guiding section, and an axial guiding sleevebleeder duct in communication with a pilot valve housing bleeder duct,the lower tube section cooperates with the relay valve interior valveseat arrangement to guide air flowing through the guiding sleeve bleederduct to the bleeder connection, and the lower tube section includesouter reinforcing ribs.
 21. The electropneumatic control valve accordingto claim 20, wherein the ribs include a plurality of axial ribs disposedat substantially equal distances from one another about the outerperiphery of the lower tube section.
 22. The electropneumatic controlvalve according to claim 21, wherein the plurality of axial ribscomprise at least four axial ribs.